Case-Control Study of Breast Cancer (Toronto)

Objectives

To evaluate the associations of oral contraceptive use, alcohol consumption, and other factors with the risk of breast cancer.

To examine certain aspects of case-control study methodology by obtaining interviews on hospital and community controls in the same study.

Methods

This case-control study was conducted in Toronto in collaboration with Dr. A. E. Clarke of the Ontario Cancer Treatment and Research Foundation. Women under 70 years of age with breast cancer diagnosed within the past six months were identified from records at the Princess Margaret Hospital. Two women matched on decade of age and residence and were selected for each case in a systematic way from census and voting files. Cases and controls were interviewed at home. For the last 214 cases, a hospital control series was interviewed as well at home.

Results

Alcohol consumption and oral contraceptive use were not materially associated with the risk of breast cancer. There were insufficient cases among young women to assess the influence of current oral contraceptive use.